Ethanol as a fuel supplement (could be additive, but not accurate in practice) could be redeemed by the research and development done by D.R. Cohn, L Bromberg and the estimable J.B. Heywood at the Massachusetts Institute of Technology.

Rather than mandate as in the command from government to add 10% ethanol to every gallon of retail gasoline sales, the gentlemen at MIT set out to use ethanol in the optimal form from an engineer’s point of view. The results crush the offerings of a vast array of alternative technologies.

Direct Ethanol Injector Positioning. Click image for more.

Direct Ethanol Injector Positioning. Click image for more.

The technology is to inject a bit of ethanol at the right moment directly into the combustion chamber to cool the compressed air and fuel mix. Gasoline is volatile, much more so than diesel, which becomes self-igniting under high enough pressures and temperatures. When those moments occur, they are known to engine folks as pre-ignition or engine knock to the consumer driver. Computer controls have eliminated the events out of existence in recent automobiles, but the engineers have known for decades that higher compressions and temperatures would lead to large efficiency gains.

With little more than an added fueling kit for the ethanol injection the scientists have been able to gain 30% in efficiency that could translate to better than 25% reduction in the gasoline needed and in turn CO2 releases.

It’s all about compression. Diesels ignite the fuel with only the heat of the compression, a major factor in their efficiency. This might be a reasonable, multiyear path to the time when alternative fuels are abundant in the market. Think of it as a transition system that uses the resources at hand. Methanol also can be used.

The problem for gasoline is high compression isn’t easy to compensate for. Decades came and went with lead added to gasoline to inhibit pre-ignition. MTBE was used, and now ethanol in bulk is used. Without some restraint, gasoline isn’t especially easy to get to high efficiency – a not well-understood fact.

Directly injecting the ethanol at the right moment in small amounts can have a huge impact on gasoline engines. Compression ratios can be raised dramatically gaining the efficiency of diesel. That allows downsizing, using much less fuel to do the same work with equal power.

Heywood is the instructor of many engine designers and engineers across the spectrum of the power system world. This influence bodes well for the results. Heywood, who is in a position to know and ask the right people offers that adaptation costs would come in at $600 or so per engine, more than a conventional low compression engine and way less than a diesel. Moreover his research adds little to the current structure of fuel delivery and sales. Its thought that the straight ethanol fill up could be every 20,000 miles. One can still use the ethanol gasoline blends for the gasoline portion of the fuel supply.

The costs are in a second fuel system to inject the ethanol and store it separately. Sensors, pumps and such bits are available at low cost. What isn’t available for long life use is the injector that would need some development to cope with the temperatures, which are higher in gasoline combustion. This shouldn’t be an issue.

Direct Ethanol Injection Boosting solves the pre-ignition issue so making the smaller engine viable with its attendant saving across the board from materials consumed in building to simple small size efficacy at low power demands.

The technology has another attribute – the injection event itself cools the fuel and air charge. As with a diesel, engines can be designed so they will self ignite thus the group offers that ethanol could be injected at 100% rates. The net effective octane rating in an injection system that is well managed would be 130 octane or better.

Those kinds of changes are really a revolution. Engines would only need to be one half the current size to produce the same power. Turbo charging, a common technology that has been driven out by emissions demands would find its way back into use, bringing with it those incredible fuel saving and power production effects.

In a more common language the system leverages the ethanol to maximize the value of the gasoline. Ethanol is hydrogen rich with oxygen that acts as an ignition inhibitor; it dries and cools by absorbing heat when sprayed into an environment.

From the report, “For an ethanol/gasoline energy consumption ratio of 10% over a drive cycle, gasoline consumption could be reduced by approximately 31% with approximately 25% coming from higher engine efficiency. If adequate ethanol is available and a greater reduction in gasoline consumption is desired, the fraction of ethanol used can be increased.”

Two more points of interest. The ethanol destined for direct injection need not be de watered completely, thus that small fueling fraction wouldn’t be as expensive. The other point is that lesser grades of gasoline are useful again making its cost also lower.

There is one more problem. The direct ethanol injection boosted engine will need substantial strengthening, much closer in design to the diesel for crankshafts, bearings and cylinder head fastening. Not much of a problem, but as GM learned when converting a gasoline engine to diesel, this deserves a full optimal design over a redesign.

It will take some time if the design makes it to market. The injector issue needs work and the full structure of basic design to prototype vehicles would have to be completed before any production vehicles are sold. But its very likely that intense thought is being given across the automotive industry. No revolution, here, but a huge jump in evolution.

The proposed numbers in efficiency are strikingly similar to gasoline hybrid technology. But the costs are one half to less than one third less to implement.

The competition is on. The technology is already out to Ethanol Boosting Systems, LLC with collaboration with Ford ongoing – others cannot be far behind. There’s a bit-o-life in the internal combustion engine after all. That has to be a relief to millions across the world.


1 Comment so far

  1. BILL HANNAHAN on April 28, 2009 2:53 PM

    A better approach would be to build a computer controlled diesel engine using direct injection of any liquid fuel with a timing and rate that produces the optimum cylinder pressure as a function of crankshaft position.

    It would require only one fuel system and would provide high thermodynamic efficiency with any fuel or mix of fuels.

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