I'll work it out for you tomorrow after I've done some main work. I map out how I will calculate in the morning.
It's not that trivial and runs something like this, with these assumptions: A) Big tank, connected by isolating valve to small cylinder of the engine. B) Consider run between tank and cylinder is small (no volume) but we can ascribe temperature to both tank and cylinder. 1) Cylinder TDC no volume for argument's sake. Start at P1 V1 T1 Expand adiabatically (quick) to P2 V2 T2 Calculate the work 2) Middle, P2 V2 T2 Isolate tank. So tank at P2 V1 T2 Cylinder at P2 V2a T2 V2a = V2 - Vtank = V2 - V1 Let cylinder expand adiabatically to P3 V3 T3 Calculate the work. This is part of the engine output 3) Bottom. Let cylinder vent to atmosphere so Pa V4 T4 in another adiabatic (quick process) Calculate the work. This is the remainder of the engine output So the above is like the little kernel of a subroutine to calculate output in ONE cycle if you know the end points. The assumptions about adiabatics and polytropic processes I need to watch carefully. Both tank and cylinder run cold below Ta (ambient). Let's say the tank is lagged. The cylinder isn't and has a heat flux coming in from Ta. Let's say it reaches some STEADY temperature below Ta but above Ttank. Run the calculation and see how the tank cools and see how the power output of the engine falls in time. Now model some heat flux into the tank at STEADY state and run the steady state calculations between start conditions and end to work out the engine power. Now see how with regenerative braking that in stop-start situations we can raise the temperature of the tank and recover waste energy. It arrests it tendency to get colder and colder as it does work there by prolonging the lifetime of the charge. You've seen it say when you empty a calor gas cylinder it gets a crust of ice around it (also liquid to gas phase change). If the cylinder is warm the gas will spew out faster and that is what is driving the compressed air engine. It's a little bit involved but if you have the engineering intuition you have probably seen what I'm getting at already but if you are Jones has-Beene-never-was you just insult people to gain cheap points. -----Original Message----- From: Michael Foster [mailto:[EMAIL PROTECTED] Sent: 28 October 2008 22:30 To: vortex-l@eskimo.com Subject: RE: [Vo]:Tata Motors - full of compressed air! I take it none of you guys has been in Indian traffic or seen the typical vehicle mix. A compressed air car would be perfect for India. Even on the highways the speed limit is 60 kph, roughly 40 mph. It's never that high in the cities. Imagine the type of traffic you get when no one pays any attention to the marked traffic lanes except the sacred cattle who line up facing the flow of vehicles, looking rather placid and pleased with themselves. It's not unusual to see a family of five riding a motor scooter. Combine that with the autorickshaws with a capacity of four but stuffed with up to 20 people and various animal powered carts in addition to conventional autos, and you can imagine that the traffic doesn't move too fast. Any vehicle that could start and stop in such traffic without the inefficiencies of an ICE would be a boon to the average Indian citizen and without the expense of a hybrid. The reduction in air pollution would be an improvement in the major cities, where most of the small cars are diesel powered. M.
