<HTML>Gentlemen,
I’m not trying to take sides one way or the other, but regarding diesels, you have to separate the old tech from the new. And yes I know that though old paradigms are hard to break, you need to open you mind to the newest technologies that are happening in the diesel world. The biggest thing going for the new generation diesels is the very high pressure of up to 25,000 + PSI, single rail electronic fuel injector systems. Unlike the lower pressure mechanical system, these high-pressure systems permit the fuel droplet size to be extremely atomization to less than 10 microns. When fuel in not broken down to these very small fuel droplet sizes of say 10 microns, only the outer valance is oxidized in the combustion process and the center of the fuel droplet is left unconsumed (oxygen cannot reach the center) in the combustion process --- and is the source of the old diesels belching black shoot or particulates as they are called.
Also the old mechanical diesels systems had to inject their entire volume of fuel in the combustion chambers at once, typically around 15 degrees BTDC so the peak pressure would be in place at around 15 degrees ATDC. This lead-time is required to permit the combustion gases to expansion in time, so the rod angularity would be in the right position to push on the crank. This put enormous strain on the mechanical components and is the main reasons why diesels were so heavy and/or robust so as to contain these very high TDC peak pressure. These very high peak pressures also produced the diesel knock that you hear and is the main source of the high NOX that diesel are famous for.
With the new high pressure system, not only can they atomized the fuel better, the electronic injector response time are so fast that they can multi pulse the injector in a single 180 power cycle at 2,000 RPM. They inject fuel at the same 15 degrees before BTDC, but only use about 20% of the fuel charge to reduce the peak pressure at TDC (why the new diesels are so quite) and then following the piston down the bore with up to 6 addition partial injection of fuel to attempt to keep a constant pressure on the piston. Almost sound like a steam engine doesn’t it. At any rate, they are already into the second generation of these systems with pizeo electronic injector that permit these extremely fast modulation rates.
Though all of these advantages of high-pressure, electronic fuel injection produce less particulates and NOX, these so equipped diesels still give high (but not as much) levels of particulates and NOX. One of the reasons are that they have to heavily boost the engine thought turbo changing to make good power. They do have the technology to control the NOX, it’s simple selecting the best cost effective technologies to use and things like injecting Urea as one of them. Take a look at [
www.dieselnet.com] is will tell you more of what I’m trying to talk about.
What I think that you have to understand is the first law of thermodynamics, which states; that energy cannot be made or destroyed, but just changes its form. That the so-called clean tail pipe emissions and any burning of any fossil based fuels produce Carbine dioxide (CO2). That the CO2 is the direct conversion of the carbon in all of the hydrocarbon based fuel that we are now using. And that diesels use less fuel to do the job is based not only on fuel conservation but the general reduction of CO2. The newest EPA requirements will introduce CO2 limits that encompass these areas. As you may know, CO2 is labeled with the green house effect with is arguably a bigger problem then the standard clean air requirements.
Whether you like it or not, diesels are the most fuel-efficient prime movers yet to date. I think that you will all enjoy checking out this site [
www.bath.ac.uk] as it shows you the most powerful (at 108,920 HP) and the most fuel efficient (at a BSFC of .026) engine in the world today with a claimed energy thermal conversion efficiency of over 50%. I wouldn’t want to put it into a car, but it shows you what level of efficiency can be reached.
It’s a complicated matrix and it will stay controversial for some time as only history will tell who is right or wrong regarding the approach to any type of energy utilization with all of it’s ramifications.
Al</HTML>