Emission Control Systems

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Safety Statement

Information and Administration: The course will start each day at 9.00am and finish at 5:00pm each day. Lunch and refreshments will be provided at the times advised by the training instructor. Workshop Safety • It will be expected that all necessary workshop health and safety procedures are followed e.g. the wearing of suitable work wear, safety footwear, eye and ear protection when in the practical workshops is mandatory. We recommend that barrier cream and workshop gloves are used at all times. • Ensure that you are fully aware of the emergency stop procedure for any of the rotating equipment used during the course. While working on rotary test equipment or engines, please ensure that all loose clothing is secure and can not get caught in the equipment or engine parts.

Introduction

Fire Escape Smoking Areas Toilets Mobile Phone, please switch off or on silent

Group introductions…..

Contents

Petrol

Diesel

Emissions

Emission Control

- EGR (Exhaust Gas Recirculation) - Oxidisation Catalyst - DPF (Diesel Particulate Filter) - FAP (Eloys + Cerine) - SCR (Selective Catalytic Reduction)

- EGR (Exhaust Gas Recirculation) - 3-Way Catalytic Converter - Lambda Sensors - PPF (Petrol Particulate Filter)

Emissions Control

What is emissions control? In terms of automotive technology, emissions control refers to the management of engine systems to utilise fuel as efficiently as possible whilst keeping harmful emissions as low as possible. In conjunction with management, emissions aftertreatment plays a significant role in this process .

Emissions Control

Emissions control systems include:

Engine management

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High Pressure Fuel Systems

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EVAP Emissions Control

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Exhaust Gas Recirculation

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Catalytic Converters

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Diesel Particulate Filters

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NOx Storage Catalysts

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Selective Catalytic Reduction

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Petrol Systems

Fuel Emissions

Key differences in Petrol and Diesel emissions:

Emissions Control Regardless of the engine fuel type, it can be argued that Engine Management technology has had the greatest impact on Emissions Control in vehicle technology. Precise management of all engine running aspects. Accurate measurements of:

Speed

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Pressure

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Temperature

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Positions

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Emissions

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Emissions Control These measurements are relayed to a management control unit so it can determine if, how and when engine actuators operate. Actuators such as:

Fuel injectors

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Ignition system

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Intake air

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Variable valve timing

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Fuel pressure

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Cooling

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EGR (Exhaust Gas Recirculation) EGR function is to reduce combustion temperature to reduce oxides of nitrogen – Nox. Created when combustion takes place with an excess of air and at very high temperatures. Oxygen combines with nitrogen and converts into nitrogen oxide (NO) and nitrogen dioxide (NO2) . Combustion temperature of 1370°C is required before NOx is formed.

EGR (Exhaust Gas Recirculation) EGR in Petrol vehicles is a key element in reducing NOx formation from excessive combustion temperatures. Petrol engine EGR has just as much functionality as it’s diesel counterpart but more so in recent years with the introduction of such fuel systems as: GDI (Gasoline Direct Injection) and Lean Burn enabled vehicles. With the event of Lean Burn type petrol engines such as FSI, TSI, TTC-L, MVV etc, we must remember the after-

effect of introducing a lean air/fuel mixture. If we are running lean, we are running hot. This in turn, has a dramatic effect on combustion temperatures.

How Does a Catalyst Work?

Catalyst: a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change. A catalytic converter works off a very simple principal that we can induce a chemical change in a substance by introducing elements that either oxidise or de-oxidise harmful emissions to change their state. Imagine the basic principals of metals oxidising . Steel, Iron, Aluminium, Copper, Zinc etc..

What happens when they oxidise? This principal is used in an automotive catalytic converter to either split oxygen/elements or combine oxygen/elements in a particular emission to make it less harmful.

How Does a Catalyst Work?

Tech Talk!

Let’s take a look at how this is achieved :

Reduction Bed (Rh)

Combination Bed (Pt + Pl)

How Does a Catalyst Work? In automotive terms, there are different Catalysts for different functions. -Diesel vehicles use a 2-Way Oxidation Catalyst to Oxidise Carbon Monoxide. -Petrol vehicles use a 3-Way Catalyst for the additional function of converting Nitric oxide and Nox -Nox absorbent catalysts convert Oxides of Nitrogen into N2 and Co2 -Particulate Filters convert soot Particulate matter into Co2 -Selective Catalytic Reduction Catalysts use AdBlue to convert NOx into ???

Operation of the Catalytic Converter

This illustration shows a typical graph of catalytic performance over the normal range of operating temperature, 100–600 ° C. Until the incoming gases have heated the catalyst to around 250–300 ° C, the activity of the catalyst is low. This temperature, at which the efficiency of the catalyst rapidly increases, is known as the light-off temperature . Until this temperature is reached, the catalyst is not working at full efficiency, and so CO, NO x and hydrocarbons will all be emitted from the exhaust pipe in significant amounts. This problem is known as cold start . Ideally the light-off temperature should be as low as possible.

Operation of the Catalytic Converter

The effect of changing air/fuel ratio on the levels of NO x (solid green), CO (black) and HC (dotted green) produced in the engine. The diagram also shows qualitatively how the engine power output changes with the A/F ratio. A general relationship between levels of CO, HC and NO x released from the engine and the A/F ratio is shown in the graph. At A/F ratios somewhat above stoichiometric (14.7:1) – that is, when the engine is operating under fuel-lean , net oxidising conditions – low levels of HC and CO are produced in the engine, and there is a peak in NO x concentration. At higher A/F values, NO x falls, but the hydrocarbon concentration increases as the engine begins to misfire.

Operation of the Catalytic Converter

Key Concepts

1. An air/fuel mixture of 14.7:1 is the best compromise, but it does not provide perfect combustion. 2. A 14.7:1 mixture gives the lowest CO and HC levels, but it also produces very high NOx levels. 3. A 3. 14.7:1 mixture also results in low oxygen levels.

Misfire

Single cylinder misfires are completely ignored by the traditional 5-gas graph. Partial misfires that are not related to an overall lean condition are also ignored. The following chart can be very useful in helping to identify single cylinder misfires and partial misfires.

This chart serves to remind us what really happens to the exhaust emissions when a single cylinder misfire or partial misfire occurs.

Example 1: one fouled spark plug on a four-cylinder engine. Three “normal” cylinders + one “no spark” cylinder

CO2 = {3(15.0%) + 1(0.0%)} divided by 4 = 11.25% CO2

CO = {3(0.5%) + 1(0.0%)} divided by 4 = 0.375% CO

HC = {3(20 ppm) = 1(6000 ppm)} divided by 4 = 1515 ppm HC

O2 = {3(0.5%) + (1(20%)} divided by 4 = 5.375% O2

Lambda/Oxygen Sensors • A Narrow Band Lambda Sensor is a sensor that measures engine exhaust emissions to ascertain how efficiently the air/fuel mixture is burning. This particular sensor only reads three mixture formations Rich, λ0 or Lean.

• 1-4 Wire Sensor

• Operating temp is +300 ℃

• Signal changes abruptly.

• A rich mixture surges voltage to approx. 0.9 volts .

• A lean mixture drops voltage down to 0.1 volts.

Narrow Band Lambda Sensor

Lambda/Oxygen Sensors

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℃

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Wideband Lambda Sensor

Lambda/Oxygen Sensors

Wide Band Lambda

NOx Storage Catalyst (NSC) As mentioned previously, Oxides of

Nitrogen (NOx) have become a growing concern in petrol vehicles, particularly Direct Injection petrol (GDI) vehicles equipped with Lean-Burn capabilities. To deal with this issue, these vehicles are fitted with an additional in-line catalyst to absorb, store and convert NOx into Co2. This system completes the conversion process under a rich regeneration process, combining NOx with Carbon Monoxide to form N2 and Co2

Petrol Particulate Filter (GPF / PPF) Gasoline Particulate or Petrol Particulate Filters are the latest advancements in petrol emissions technology and offer similar functionality to it’s diesel counterpart, the DPF,

Whilst this technology has only began to be introduced recently, you will see this technology fitted to the likes of high-end, high- performance vehicles such as Porsche

Petrol Particulate Filter (GPF / PPF)

With the same intended principals as the DPF, The PPF’s function is to convert harmful soot particles into Co2. The same ceramic monolith structure is used to capture particulate matter, hold it and burn it off in a regeneration process which converts it into Carbon Dioxide. Particulate Matter has become a growing concern in petrol vehicles as emissions

standards become even tighter. The main concern lies within the

inconsistency of fuel quality around the globe. Countries with poor fuel quality of low Octane and high Sulphur content.

Workshop Practical: Petrol

Emissions Control Overview

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Key Components Overview

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Live Emissions Testing

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Diagnostic Procedures

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Recap + Q&A Session

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Diesel Systems

Diesel Emissions

What is the issue with Diesel?

Diesel is a unique fuel that poses broad areas of concern.

As a fuel, it is not as volatile as petrol. It is a slow burning fuel with a slow and prolonged release of energy that is only suitable for Compression Igniton (CI) engines. Its refinement is crude and requires additional lubricant to protect the engines high pressure fuel injection components.

These carachteristics make diesel emissions very different to its petrol counterpart.

Diesel Emissions Areas of Concern:

Due to the carachteristis of diesel fuel, there are key areas of it’s emissions we need to address.

Carbon Monoxide (CO)

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Carbon Dioxide (CO2)

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Soot/Particulate Matter (PM)

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Oxides of Nitrogen (NOx)

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Diesel Emissions

Key differences in Diesel emissions:

EGR (Exhaust Gas Recirculation) Precise control of EGR.

The amount of exhaust gas to recirculate must be controlled by the engine control unit, so that there is not an increase in the emissions of hydrocarbons (HC) , carbon monoxide (CO) and soot particulates (PM)

EGR (Exhaust Gas Recirculation) Issues associated with EGR (Diesel):

Carbon build up/blockages are the biggest threat to the efficiency of the EGR system.

This issue is mainly caused by recirculating hot exhaust gasses back into a cold intake. In this issue the carbon content in the gas solidifies and forms in the EGR valve itself, the intake manifold and the intake ports. Temperature control of the recirculated exhaust gas is key to reducing this issue.

EGR (Exhaust Gas Recirculation)

EGR (Exhaust Gas Recirculation) Additional Exhaust Gas Recirculation.

Oxidation Catalyst (2-Way Catalyst) Due to the nature of a diesel engines physical workings, an oxidation catalyst is fitted as a conventional 3-way petrol catalyst does not function the same way. As a diesel engine expels large amounts of oxygen through the exhaust, we have high levels of Carbon Monoxide to convert in the presence of this Oxygen. The Oxygen itself impedes the conversion of NOx into Nitrogen and Oxygen. Hydrocarbons, Carbon Monoxide and Sulphates must be oxidised in order to turn them into Water and Carbon Dioxide.