Diesel and gasoline engines require a lot of air as part of the internal combustion process. Anyone who has lifted the hood on their automobile knows that the air coming into a vehicle engine is filtered to keep out road dust and grit from entering the engine cylinders. All vehicles have an air filter for this purpose and these are commonly made of a paper filtration material, are housed in a plastic or metal can, and can be opened easily for filter replacement.
Military vehicles also have an engine air filter but this is a much more critical component – off road operations tend to involve much more dust and debris than normal driving and should the filter become completely clogged, the engine will stop. And you don’t want a stalled engine in the middle of a combat operation.
One way to avoid filtration problems is to measure the pressure drop across the air filter at all times during engine operation. The best design of an engine air filter is one that allows a lot of air to pass with a minimum loss of pressure, and a lot of effort goes into filter design that can provide a large surface area in a small space – even an ordinary air filter contains dozens of folds to achieve this. But the danger of a filter clogging is too great and the best method of determining how well a filter is operating is to directly measure the pressure drop across it.
The pressure drop across a working air filter is often very small – on the order of a few hundred Pascals, especially at low engine RPM – so a pressure sensor for this purpose must be sensitive to very low pressures. In addition, the pressure transducer must be rugged enough to function well under the hood of a vehicle where shock, vibration and high ambient temperatures are common.
Validyne has supplied a variant of the P55 pressure transmitter that has been designed for use in military vehicles to measure air filter pressure drop. The P55 pressure transmitter electronics has been secured with epoxy and a special housing, connector and custom mounting plate provide a sturdy attachment to the air filter enclosure. The 4-20 mA signal is used by the engine control system to alert the driver when the air filter starts to clog. This allows for preventative maintenance and a way to avoid stalling the engine in challenging conditions.
Contact an application engineer at firstname.lastname@example.org or 818-886-8488 for more information on similar applications.