FI engine cycle analysis
07-08-2004 | 05:44 PM
#1
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From: NorCal
FI engine cycle analysis
Of course, we all have a thirst for making more power, right? Most of us are looking to forced induction to solve our problems. I know I am 
. Assuming the Wankel rotary engine is utilizing the Otto cycle, how does turbocharger analysis work? Remember thermodynamics? Well, if you're a geek like myself, you might remember something called Air-Standard Brayton Cycle Analysis. It was basically a compressor, combustor, and a turbine. Also, you could add an intercooler, which is of similar function with our intercoolers (are they bar-and-plate or shell-and-tube? Most car intercoolers are bar-and-plate). There was also regenerators, but I'm not going to get into that because I don't think car engines have these. I figure I might be able to use this as a tool for sizing turbochargers. Could Air-Standard Brayton Cycle analysis be used for turbochargers? I used to think so, but now I don't, because it is completely different from Otto Cycle and/or Diesel Cycle Analysis. So, where do turbochargers fit in when it comes to Otto Cycle Analysis? On an engine's exhaust stroke, some of the exhaust gas is extracted to run the turbine, thus turning the compressor. How does this affect the overall, well ANYTHING? Personally, I'll crunch numbers (if I had the time 
) if it leads to getting the right answer, or at least something reasonable. If there is anyone that has the slightest clue what I'm talking about, please feel free to give me some 411 . The thought is burning a hole in my brain. Am I thinking too hard or what?!
. Assuming the Wankel rotary engine is utilizing the Otto cycle, how does turbocharger analysis work? Remember thermodynamics? Well, if you're a geek like myself, you might remember something called Air-Standard Brayton Cycle Analysis. It was basically a compressor, combustor, and a turbine. Also, you could add an intercooler, which is of similar function with our intercoolers (are they bar-and-plate or shell-and-tube? Most car intercoolers are bar-and-plate). There was also regenerators, but I'm not going to get into that because I don't think car engines have these. I figure I might be able to use this as a tool for sizing turbochargers. Could Air-Standard Brayton Cycle analysis be used for turbochargers? I used to think so, but now I don't, because it is completely different from Otto Cycle and/or Diesel Cycle Analysis. So, where do turbochargers fit in when it comes to Otto Cycle Analysis? On an engine's exhaust stroke, some of the exhaust gas is extracted to run the turbine, thus turning the compressor. How does this affect the overall, well ANYTHING? Personally, I'll crunch numbers (if I had the time ) if it leads to getting the right answer, or at least something reasonable. If there is anyone that has the slightest clue what I'm talking about, please feel free to give me some 411 . The thought is burning a hole in my brain. Am I thinking too hard or what?!
07-14-2004 | 01:24 AM
#4
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From: Chandler, Az
Shelleys man 06
I understand what you are saying. I'm interested in the supercharged side of things and I have the analytical tools to handle this problem statement and the background to handle the modeling. Unfortunately, I haven't had much time except on weekend to think about the modeling effort. I have captured a basic low pressure ratio compressor map that I plan on scaling in flow, pressure ratio, and efficiency to use as a basis for evaluation of the matching between an axial flow supercharger and a rotary based otto cycle which uses the flow characteristics of the Renesis. It will likely take me a couple weks to get the details worked out. However, once the model is assembled and checked out it will be very interesting to see how the performance looks and what the benefits of different intercooler designs would be.
The very basics of these cycles really only involve the application of the continuity equation, and the energy equation from basic thermo. If you want to get into the CFD world, you would typically include the momentum equations also. Most people do not want to go to that degree of detail. I will not be going down that path. However, to your basic question:
If you chose to think about the rotary engine as a black box that added heat to the picture (much like a combustor) you could arrive at the conclusion that treating the turbo with a Brayton cycle analysis should work. However, it really doesn't get us where we want to be. Jet engines (Brayton cycle machines) either produce thrust (mdot*delta Velocity) or they produce shaft power through a power turbine/gear box. There aren't any turbos out there that do this. As a result, I think you will have to treat this as a Hybrid cycle.
Start at ambient conditions, assume you draw air through the intake at ambient pressure and temperature (for improved accuracy, you could take a filter loss and adjust temperature for cooling or heating affects),
guess an airflow and a compressor speed,
from this information and the turbo compressor map you can determine the compressor exit pressure and temperature,
then depending on whether you have an intercooler or not, you either hold temperature approximately constant or take a intercooler temperature drop (based on the intercooler effectiveness maps). You also account for either the duct pressure drop or the intercooler and duct pressure drop to get to the intake. Note: your assumptions may not be correct yet.
Then you need to identify what speed the engine is running at and identify the appropriate volumetric efficiency to determine how much airflow the Renesis is willing to swallow at the combination of speed, pressure, and temperature you're at.
Then you need to complete the associated Otto cycle calculations as if the engine was operating at the inlet pressure and temperature and exit pressure and temperature of the turbocharged system. Again we have to make some assumptions about the exit back pressure that would exist. (We will close the loop on this in the matrix solution)
Now I have some estimate of the exit pressure, temperature, and air-fuel mixture exiting the Renesis exhaust manifold.
This mixture is going to flow through the turbine. I would use the turbine map to determine the corresponding pressure drop, power output, temperature drop, etc
Of course the turbine power and the compressor power will have to balance out (ignoring mechanical losses for the time being) and this will help us determine what the correct turbocharger speed will be through iteration.
Additionally, the turbine pressure ratio which will affect the available turbine power will be influenced by the remaining catalytic converter, piping, and muffler pressure losses.
Once I get back to ambient, I can balance all of the associated equations and drive all of the starting guesses to the converged solution.
Note: This is very different from the classic Brayton cycle in that the Renesis engine will determine how much flow it is capable of swallowing at any one combination of speed, pressure and temperature. This will play into the match point speed, pressure ratio, temperature, efficiency, and surge margin of the turbo charger wheel/ compressor. Normally this throttling characteristic is defined by the turbine map and nozzle flow area. While they still have an influence, the true throttling is determined by the mass flow behavior of the Renesis engine versus speed, pressure, and temperature.
Hope this isn't too basic and that it helps in some small way.
Regards
I understand what you are saying. I'm interested in the supercharged side of things and I have the analytical tools to handle this problem statement and the background to handle the modeling. Unfortunately, I haven't had much time except on weekend to think about the modeling effort. I have captured a basic low pressure ratio compressor map that I plan on scaling in flow, pressure ratio, and efficiency to use as a basis for evaluation of the matching between an axial flow supercharger and a rotary based otto cycle which uses the flow characteristics of the Renesis. It will likely take me a couple weks to get the details worked out. However, once the model is assembled and checked out it will be very interesting to see how the performance looks and what the benefits of different intercooler designs would be.
The very basics of these cycles really only involve the application of the continuity equation, and the energy equation from basic thermo. If you want to get into the CFD world, you would typically include the momentum equations also. Most people do not want to go to that degree of detail. I will not be going down that path. However, to your basic question:
If you chose to think about the rotary engine as a black box that added heat to the picture (much like a combustor) you could arrive at the conclusion that treating the turbo with a Brayton cycle analysis should work. However, it really doesn't get us where we want to be. Jet engines (Brayton cycle machines) either produce thrust (mdot*delta Velocity) or they produce shaft power through a power turbine/gear box. There aren't any turbos out there that do this. As a result, I think you will have to treat this as a Hybrid cycle.
Start at ambient conditions, assume you draw air through the intake at ambient pressure and temperature (for improved accuracy, you could take a filter loss and adjust temperature for cooling or heating affects),
guess an airflow and a compressor speed,
from this information and the turbo compressor map you can determine the compressor exit pressure and temperature,
then depending on whether you have an intercooler or not, you either hold temperature approximately constant or take a intercooler temperature drop (based on the intercooler effectiveness maps). You also account for either the duct pressure drop or the intercooler and duct pressure drop to get to the intake. Note: your assumptions may not be correct yet.
Then you need to identify what speed the engine is running at and identify the appropriate volumetric efficiency to determine how much airflow the Renesis is willing to swallow at the combination of speed, pressure, and temperature you're at.
Then you need to complete the associated Otto cycle calculations as if the engine was operating at the inlet pressure and temperature and exit pressure and temperature of the turbocharged system. Again we have to make some assumptions about the exit back pressure that would exist. (We will close the loop on this in the matrix solution)
Now I have some estimate of the exit pressure, temperature, and air-fuel mixture exiting the Renesis exhaust manifold.
This mixture is going to flow through the turbine. I would use the turbine map to determine the corresponding pressure drop, power output, temperature drop, etc
Of course the turbine power and the compressor power will have to balance out (ignoring mechanical losses for the time being) and this will help us determine what the correct turbocharger speed will be through iteration.
Additionally, the turbine pressure ratio which will affect the available turbine power will be influenced by the remaining catalytic converter, piping, and muffler pressure losses.
Once I get back to ambient, I can balance all of the associated equations and drive all of the starting guesses to the converged solution.
Note: This is very different from the classic Brayton cycle in that the Renesis engine will determine how much flow it is capable of swallowing at any one combination of speed, pressure and temperature. This will play into the match point speed, pressure ratio, temperature, efficiency, and surge margin of the turbo charger wheel/ compressor. Normally this throttling characteristic is defined by the turbine map and nozzle flow area. While they still have an influence, the true throttling is determined by the mass flow behavior of the Renesis engine versus speed, pressure, and temperature.
Hope this isn't too basic and that it helps in some small way.
Regards
07-14-2004 | 02:13 AM
#5
mostly harmless
Joined: Jun 2002
Posts: 3,440
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From: Greater Vancouver Area, BC
too basic?? man, that's a whole lot more complex than it has to be...i can relate to understanding what it is you're trying to build, but it can be a whole lot easier than that.
look at a compressor map, Turbonetics (Garett clones) have 'em for the size you're looking for (T04/60 series, as well as every other turbo they make). then figure out the A/R ratio you're looking for (for a 13B, the standard is between .8 and 1.2, with the lag obviously lower on the smaller end, and rediculous on the higher end).
look at a compressor map, Turbonetics (Garett clones) have 'em for the size you're looking for (T04/60 series, as well as every other turbo they make). then figure out the A/R ratio you're looking for (for a 13B, the standard is between .8 and 1.2, with the lag obviously lower on the smaller end, and rediculous on the higher end).
07-14-2004 | 03:29 AM
#6
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Joined: Feb 2004
Posts: 344
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From: Belgique
Originally Posted by Turbine_pwr
I understand what you are saying. I'm interested in the supercharged side of ...
Hope this isn't too basic and that it helps in some small way.
Regards
I'm intending to build a model for the Renesis engine but with no experience in modeling, it's going to be a steep learning curve.
Thanks
IKN
07-14-2004 | 09:01 AM
#7
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From: NorCal
Originally Posted by Turbine_pwr
Shelleys man 06
I understand what you are saying. I'm interested in the supercharged side of things and I have the analytical tools to handle this problem statement and the background to handle the modeling. Unfortunately, I haven't had much time except on weekend to think about the modeling effort. I have captured a basic low pressure ratio compressor map that I plan on scaling in flow, pressure ratio, and efficiency to use as a basis for evaluation of the matching between an axial flow supercharger and a rotary based otto cycle which uses the flow characteristics of the Renesis. It will likely take me a couple weks to get the details worked out. However, once the model is assembled and checked out it will be very interesting to see how the performance looks and what the benefits of different intercooler designs would be.
The very basics of these cycles really only involve the application of the continuity equation, and the energy equation from basic thermo. If you want to get into the CFD world, you would typically include the momentum equations also. Most people do not want to go to that degree of detail. I will not be going down that path. However, to your basic question:
If you chose to think about the rotary engine as a black box that added heat to the picture (much like a combustor) you could arrive at the conclusion that treating the turbo with a Brayton cycle analysis should work. However, it really doesn't get us where we want to be. Jet engines (Brayton cycle machines) either produce thrust (mdot*delta Velocity) or they produce shaft power through a power turbine/gear box. There aren't any turbos out there that do this. As a result, I think you will have to treat this as a Hybrid cycle.
Start at ambient conditions, assume you draw air through the intake at ambient pressure and temperature (for improved accuracy, you could take a filter loss and adjust temperature for cooling or heating affects),
guess an airflow and a compressor speed,
from this information and the turbo compressor map you can determine the compressor exit pressure and temperature,
then depending on whether you have an intercooler or not, you either hold temperature approximately constant or take a intercooler temperature drop (based on the intercooler effectiveness maps). You also account for either the duct pressure drop or the intercooler and duct pressure drop to get to the intake. Note: your assumptions may not be correct yet.
Then you need to identify what speed the engine is running at and identify the appropriate volumetric efficiency to determine how much airflow the Renesis is willing to swallow at the combination of speed, pressure, and temperature you're at.
Then you need to complete the associated Otto cycle calculations as if the engine was operating at the inlet pressure and temperature and exit pressure and temperature of the turbocharged system. Again we have to make some assumptions about the exit back pressure that would exist. (We will close the loop on this in the matrix solution)
Now I have some estimate of the exit pressure, temperature, and air-fuel mixture exiting the Renesis exhaust manifold.
This mixture is going to flow through the turbine. I would use the turbine map to determine the corresponding pressure drop, power output, temperature drop, etc
Of course the turbine power and the compressor power will have to balance out (ignoring mechanical losses for the time being) and this will help us determine what the correct turbocharger speed will be through iteration.
Additionally, the turbine pressure ratio which will affect the available turbine power will be influenced by the remaining catalytic converter, piping, and muffler pressure losses.
Once I get back to ambient, I can balance all of the associated equations and drive all of the starting guesses to the converged solution.
Note: This is very different from the classic Brayton cycle in that the Renesis engine will determine how much flow it is capable of swallowing at any one combination of speed, pressure and temperature. This will play into the match point speed, pressure ratio, temperature, efficiency, and surge margin of the turbo charger wheel/ compressor. Normally this throttling characteristic is defined by the turbine map and nozzle flow area. While they still have an influence, the true throttling is determined by the mass flow behavior of the Renesis engine versus speed, pressure, and temperature.
Hope this isn't too basic and that it helps in some small way.
Regards
I understand what you are saying. I'm interested in the supercharged side of things and I have the analytical tools to handle this problem statement and the background to handle the modeling. Unfortunately, I haven't had much time except on weekend to think about the modeling effort. I have captured a basic low pressure ratio compressor map that I plan on scaling in flow, pressure ratio, and efficiency to use as a basis for evaluation of the matching between an axial flow supercharger and a rotary based otto cycle which uses the flow characteristics of the Renesis. It will likely take me a couple weks to get the details worked out. However, once the model is assembled and checked out it will be very interesting to see how the performance looks and what the benefits of different intercooler designs would be.
The very basics of these cycles really only involve the application of the continuity equation, and the energy equation from basic thermo. If you want to get into the CFD world, you would typically include the momentum equations also. Most people do not want to go to that degree of detail. I will not be going down that path. However, to your basic question:
If you chose to think about the rotary engine as a black box that added heat to the picture (much like a combustor) you could arrive at the conclusion that treating the turbo with a Brayton cycle analysis should work. However, it really doesn't get us where we want to be. Jet engines (Brayton cycle machines) either produce thrust (mdot*delta Velocity) or they produce shaft power through a power turbine/gear box. There aren't any turbos out there that do this. As a result, I think you will have to treat this as a Hybrid cycle.
Start at ambient conditions, assume you draw air through the intake at ambient pressure and temperature (for improved accuracy, you could take a filter loss and adjust temperature for cooling or heating affects),
guess an airflow and a compressor speed,
from this information and the turbo compressor map you can determine the compressor exit pressure and temperature,
then depending on whether you have an intercooler or not, you either hold temperature approximately constant or take a intercooler temperature drop (based on the intercooler effectiveness maps). You also account for either the duct pressure drop or the intercooler and duct pressure drop to get to the intake. Note: your assumptions may not be correct yet.
Then you need to identify what speed the engine is running at and identify the appropriate volumetric efficiency to determine how much airflow the Renesis is willing to swallow at the combination of speed, pressure, and temperature you're at.
Then you need to complete the associated Otto cycle calculations as if the engine was operating at the inlet pressure and temperature and exit pressure and temperature of the turbocharged system. Again we have to make some assumptions about the exit back pressure that would exist. (We will close the loop on this in the matrix solution)
Now I have some estimate of the exit pressure, temperature, and air-fuel mixture exiting the Renesis exhaust manifold.
This mixture is going to flow through the turbine. I would use the turbine map to determine the corresponding pressure drop, power output, temperature drop, etc
Of course the turbine power and the compressor power will have to balance out (ignoring mechanical losses for the time being) and this will help us determine what the correct turbocharger speed will be through iteration.
Additionally, the turbine pressure ratio which will affect the available turbine power will be influenced by the remaining catalytic converter, piping, and muffler pressure losses.
Once I get back to ambient, I can balance all of the associated equations and drive all of the starting guesses to the converged solution.
Note: This is very different from the classic Brayton cycle in that the Renesis engine will determine how much flow it is capable of swallowing at any one combination of speed, pressure and temperature. This will play into the match point speed, pressure ratio, temperature, efficiency, and surge margin of the turbo charger wheel/ compressor. Normally this throttling characteristic is defined by the turbine map and nozzle flow area. While they still have an influence, the true throttling is determined by the mass flow behavior of the Renesis engine versus speed, pressure, and temperature.
Hope this isn't too basic and that it helps in some small way.
Regards
. Complicated question, perfect answer. What more could I ask for? Welcome to the club .
07-14-2004 | 09:03 AM
#8
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From: NorCal
I am glad that this thread has been kept alive . The engineering aspect of this engine is such an interesting subject. I had completely forgotten about hybrid cycles; when I took thermodynamics I, we only learned the Air-Standard Brayton cycle. I make a recommendation to do Otto Cycle and hybrid cycle analysis, but of course, my professor isn't going to cater to what one person wants. Thank you turbine_pwr. Your vast knowledge is always welcome .
. The engineering aspect of this engine is such an interesting subject. I had completely forgotten about hybrid cycles; when I took thermodynamics I, we only learned the Air-Standard Brayton cycle. I make a recommendation to do Otto Cycle and hybrid cycle analysis, but of course, my professor isn't going to cater to what one person wants. Thank you turbine_pwr. Your vast knowledge is always welcome .
07-14-2004 | 09:18 AM
#9
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From: NorCal
Wakeech is right. There are easier ways to do this other than using CFD of FEM. Heck, most tuner shops don't use any engineering whatsoever. They just send their measurements to some engineer, and in a few days, bam, they get their part! I met someone at work who owns a performance shop who quit mechanical engineering at UH. He told me he hasn't utilized one differential equation or mass balance to find anything. So, what's the point of engineering? Other than the consequence of the potential to make buttloads of cash, it provides more insight about the overall design of X-part. Mechanics are not stupid, either. In fact, there are more mechanics who know infinity-times more than any Ph.D. in mechanical engineering. It's because they live in the real world. Engineers live in the simulated.
07-14-2004 | 10:32 AM
#10
Whenever you guys want to get from sitting in front of the computer to behind the wheels of your RX's, let me know. There comes a point in all of this where two things happen; 1) The intellectual complexity with which certain problems are being handled begins to take precedence over the problem itself, otherwise known as "bench racing" and, 2) Whatever solutions/ideas are created must actually be applied on a physical level and the outcome(s) evaluated. To this end there are several companies and people who have traversed this road before, as indicated by Wakeech. Shell, I hate to say this but DO A SEARCH!! Just kidding, Man. But seriously, there are several publications that deal with all of this. I wouldn't know which ones they are because at this point I am not much interested in FI. I just couldn't help but barge in the room with my unintellectual, blue-collar, hollerin'. Hope ya understand.
Charles
Charles
07-14-2004 | 01:51 PM
#11
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From: NorCal
Understandable Charles. In fact, most people don't give a hoot about this nonsensical gibberish anyways. I love analysis, and I also love opinions, which is why I can't stay away from this forum. You can tell I love shooting the breeze when it comes to bench racing. Since I'm currently broke, I enjoy absorbing ideas from others who have the experience and knowledge.
07-15-2004 | 01:10 PM
#15
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From: Chandler, Az
Shell,
Thanks for the kind words.
Wakeech,
Of course there are simpler ways to do things and I'm aware of the family of turbocharger maps and for that matter the limited turbine maps that are available out on the net. I have modeling tools that should make it possible to build the model that I describe above. I just haven't had/taken the time to put this together yet. I do believe the model I describe would allow me to identify what will work and what will not before I make modifications to the car. The area that I am weakest in is the Otto cycle side of this. However, I believe it is manageable.
Charles,
I agree that many engineers would be happy just running numbers all the time and do not get involved enough in the fun of bending wrenches and bangin knuckles. In my present role, we do a lot of modeling, but we also, build, test, and adjust our designs to acheive the required level of performance, and life. This work is in the gas turbine field rather than automotive. I can not claim to be very knowledgeable in the automotive racing world. Clearly you and Richard have much more experience in this area than I do. Likely many of the people here do also. I do, however, feel that there is a proper balance between analysis and test. I wouldn't want to just bend metal and test... this gets too expensive and takes too much time. But you can also analyze until you're blue in the face and you still do not have any parts to test. So... enough gibberish thanks for reading my rantings
Thanks for the kind words.
Wakeech,
Of course there are simpler ways to do things and I'm aware of the family of turbocharger maps and for that matter the limited turbine maps that are available out on the net. I have modeling tools that should make it possible to build the model that I describe above. I just haven't had/taken the time to put this together yet. I do believe the model I describe would allow me to identify what will work and what will not before I make modifications to the car. The area that I am weakest in is the Otto cycle side of this. However, I believe it is manageable.
Charles,
I agree that many engineers would be happy just running numbers all the time and do not get involved enough in the fun of bending wrenches and bangin knuckles. In my present role, we do a lot of modeling, but we also, build, test, and adjust our designs to acheive the required level of performance, and life. This work is in the gas turbine field rather than automotive. I can not claim to be very knowledgeable in the automotive racing world. Clearly you and Richard have much more experience in this area than I do. Likely many of the people here do also. I do, however, feel that there is a proper balance between analysis and test. I wouldn't want to just bend metal and test... this gets too expensive and takes too much time. But you can also analyze until you're blue in the face and you still do not have any parts to test. So... enough gibberish thanks for reading my rantings
07-15-2004 | 01:38 PM
#16
Yeah, I agree, knowledge based on theory and balanced by experience or vice versa certainly beats attempting to forge new ground in areas where others have already tried and failed. As you said, it can get expensive when doing nothing more than replacing parts. I just couldn't resist being a wiseguy in splashing cold water on the discussion. You guys should listen in on the conversations my girlfriend and I have as she is a sci-fi fan. Gotta love those smart women!
Charles
Charles
07-15-2004 | 04:27 PM
#17
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From: NorCal
I have always learned to plan a million times before I even turn a wrench. I use the 90-10 rule: 90% planning, 10% actual work. Everyone here has their point to make. There is no right way to approach this; some people prefer to experiment, some prefer hardcore analysis, and some like both. Using CFD and FEA is all fun, but not all of us have access. In that kind of situation, it's best to use our intuition to make things work.
Anyways, I have a question about compressor/turbine maps. Are the efficiencies isentropic or actual? For example, the horizontal axis on a turbine map depicts the pressure ratio in terms of p[1T]/p[2S].
Anyways, I have a question about compressor/turbine maps. Are the efficiencies isentropic or actual? For example, the horizontal axis on a turbine map depicts the pressure ratio in terms of p[1T]/p[2S].
Last edited by shelleys_man_06; 07-16-2004 at 01:37 AM.
07-16-2004 | 01:22 AM
#18
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From: Chandler, Az
In the gas turbine world, both compressor efficiencies and turbine efficiencies are what should most accurately be called the adiabatic efficiency (in some circles this is also coined the isentropic efficiency). The equations are basically as follows:
Compressor efficiency = Ideal Work / Actual Work which becomes after a little bit of work
Comp Eff = ( Pr^((gamma-1)/gamma) - 1.0) / ( Tr - 1.0) where
Pr = compressor pressure ratio
Tr = compressor temperature ratio
gamma = the ratio of specific heats or cp/cv (note: these change with temp and FAR)
Turbine efficiency = Actual work / Ideal work and I'll leave the rest up to you guys.
You may also run across something called the polytropic efficiency (also known as the small stage efficiency). It is nice to use when comparing compressors with different pressure ratios because it is independant of pressure ratio(whereas the adiabatic/isentropic efficiency is not). This allows you to directly understand the technology level of the designs you are comparing.
Regards
Compressor efficiency = Ideal Work / Actual Work which becomes after a little bit of work
Comp Eff = ( Pr^((gamma-1)/gamma) - 1.0) / ( Tr - 1.0) where
Pr = compressor pressure ratio
Tr = compressor temperature ratio
gamma = the ratio of specific heats or cp/cv (note: these change with temp and FAR)
Turbine efficiency = Actual work / Ideal work and I'll leave the rest up to you guys.
You may also run across something called the polytropic efficiency (also known as the small stage efficiency). It is nice to use when comparing compressors with different pressure ratios because it is independant of pressure ratio(whereas the adiabatic/isentropic efficiency is not). This allows you to directly understand the technology level of the designs you are comparing.
Regards
07-16-2004 | 12:20 PM
#23
mostly harmless
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From: Greater Vancouver Area, BC
so, just being curious, what is it you're trying to figure out here?? just further understanding the behavour of a theoretically ideal compressor for this engine, or what??
*still watching and learning intently*
*still watching and learning intently*
07-16-2004 | 01:13 PM
#24
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From: Belgique
Shelleys,
All the stuff you need and more can be found in John B Heywood's book (bible) : Internal Combustion Engine Fundamentals, including a modus operandi for modeling simple or complex engines.
I actually bought SAE Tech Paper 912479 : A Performance Simulation for Spark Ignition Wankel Rotary Engine. Once they got the geometry model right, the authors of this paper used the same equations and models as given for piston engines in Heywood's book.
All the stuff you need and more can be found in John B Heywood's book (bible) : Internal Combustion Engine Fundamentals, including a modus operandi for modeling simple or complex engines.
I actually bought SAE Tech Paper 912479 : A Performance Simulation for Spark Ignition Wankel Rotary Engine. Once they got the geometry model right, the authors of this paper used the same equations and models as given for piston engines in Heywood's book.
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